1. Field of the Invention
This invention relates to a process for utilizing polyethylene terephthalate, especially scrap polyethylene terephthalate in the production of linear, high molecular weight copolyesters.
The growing demand for polyethylene terephthalate disposable containers such as beverage bottles has created a need to develop uses for scrap polyethylene terephthalate. The present invention provides a process for utilizing polyethylene terephthalate as a reactive intermediate in the production of copolyesters useful in the manufacture of such products as fibers, films, and other shaped objects.
2. Description of the Prior Art
Numerous patents disclose processes for utilizing scrap polyesters in polymer production such as U.S. Pat. Nos. 3,222,999, 3,344,091, 4,078,143 and 4,138,374.
In U.S. Pat. No. 3,222,299 it is stated that reclaimed monomer, obtained by heating waste polymer with glycol, may be injected into the polymerization system but must be kept below a level of about 20% of the total monomer if the polymer produced is to have satisfactory properties. When amounts of recovered monomer higher than about 20% are injected, it is found that the rate of polymerization of the mixture is reduced to such an extent that the output of the equipment must be cut back to a prohibitively low level. In the present process, 100% scrap polyester can be utilized with no loss in properties or polymerization rate. In fact, the polymerization rate is faster than the rate for the preparation of the same copolyesters from dimethyl terephthalate, ethylene glycol, and 1,4-cyclohexanedimethanol.